Aberrant B cells, autoimmunity and the benefit of targeting B cells in chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) remains the main complication of allogeneic hematopoietic stem cell transplantation, limiting its chances for a successful outcome. The over-activity of CD4+ effector T cells and the excessive production of pro-inflammatory cytokines are followed by the development of immune-mediated inflammation and fibrosis of multiple organs. This is the reason for adopting T cell targeting therapies such as cyclosporine A, tacrolimus and mycophenolate mofetil. However, 40% of treated cGVHD patients remain unresponsive, which results in increased morbidity and mortality. Given the complexity of cGVHD pathogenesis, the involvement of B cells as an important player also needs to be explored. Function of aberrant B cells and secretion of relevant cytokines such as B cell activating factor (BAFF) have been found to correlate with cGVHD severity and have therefore become therapeutic targets. Better understanding of the role of B cells and their efficient targeting could improve the outcome of cGVHD.